Fatty Acid Homologues Research Articles

Analysis of Derivatized N-Acyl Amino Acid Surfactants Using HPLC and HPLC/MS

A method for the analysis of weak anionic surfactants based on N-acyl amino acids was developed. The surfactants were derivatized using 2,4′-dibromoacetophenone yielding 4′-bromophenacyl esters suitable for spectrophotometric detection. Surfactants containing glycine, threonine and glutamic acid were analyzed after derivatization using reversed-phase liquid chromatography with UV/Vis and MS detection. The gradient profile was optimized using isocratic retention data of N-acyl-linked fatty acid homologues. The relative content of the homologues of N-acyl-linked fatty acids was expressed using the determined method. The intraday repeatability and stability of the prepared derivatives was tested. The relative content of fatty acids in the surfactants was correlated with the most common sources of fatty acids, showing high Pearson’s correlation coefficients with the typical fatty acids profile of a coconut oil.

Screening of Antagonistic Activity of Lactic Acid Bacteria Strains in relation to Candida scotti for Optimal Conservation of Plant Juices

In a model experiment on juices of legumes with nine strains of lactic acid bacteria (LAB) of the genus Lactobacillus isolated from aboveground parts of the vegetating leguminous plants (RS1, RS3, RS4), their rhizosphere (RS5), plant juices (RS6 and RS7), and a corn silage (RS2), and also with the collection strain of Lactobacillus plantarum BS933 and commercial strain Streptococcus faecium 500, joint cultivation with Candida scotti was carried out. Change of standard indicators, such as PH of the medium, the ratio of lactic acid to fatty acid homologues, and microflora analysis of the juice demonstrated that yeast actively competes with LAB for nutrients in the environment and possesses an antibacterial effect that leads to silage deterioration. The results showed that only certain Lactobacillus strains (3 of 8) and also S. faecium 500 are capable of resisting negative consequences of yeast activity during conservation of plant juices.

Organic matters and lipid biomarkers in surface sediments from the northern South China Sea: Origins and transport

In this study, content and distribution of organic matters (OM) and lipid biomarkers in surface sediments from northern South China Sea (SCS) were identified to reveal the sources and transport of fine-grained sediments. Organic matters and lipid biomarkers exhibited distinct spatial variation in northern SCS. Terrestrial discharge from the Pearl River and some mountainous rivers in southwestern Taiwan may contribute to the relatively high organic matters in the corresponding sea areas. The detection of unsaturated fatty acid homologues suggested the algal and/or bacterial OM contribution to surface sediments. The composites and distribution of lipid biomarkers indicate their mixed sources from terrestrial plants, marine algae and bacterial. Together with the proof of clay mineral composites in the sediments, the results suggested that the currents, including the Guangdong Coastal Current and Kuroshio Current, control the transport and distribution of terrestrial sediment and the sedimentary environment in the northern SCS.

Solvent-Dependent Stabilization of Metastable Monolayer Polymorphs at the Liquid–Solid Interface

Self-assembly of 1,3,5-tris(4'-biphenyl-4"-carbonitrile)benzene monolayers was studied at the liquid-solid interface by scanning tunneling microscopy. Application of different fatty acid homologues as solvents revealed a solvent-induced polymorphism. Yet, tempering triggered irreversible phase transitions of the initially self-assembled monolayers, thereby indicating their metastability. Interestingly, in either case, the same thermodynamically more stable and more densely packed monolayer polymorph was obtained after thermal treatment, irrespective of the initial structure. Again, the same densely packed structure was obtained in complementary solvent-free experiments conducted under ultrahigh vacuum conditions. Thus, self-assembly of metastable polymorphs at room temperature is explained by adsorption of partially solvated species under kinetic control. The irreversible phase transitions are induced by thermal desolvation, that is, desorption of coadsorbed solvent molecules.

A chiral high-performance liquid chromatography–tandem mass spectrometry method for the stereospecific analysis of enoyl-coenzyme A hydratases/isomerases

The enzymes catalyzing the stereospecific hydration of 2-enoyl-CoA into the corresponding S- or R-3-hydroxyacyl-CoA are named enoyl-CoA hydratases (ECH), where the S-specific is called ECH-1 and the R-specific is called ECH-2. Current ECH assays are mostly based on spectrophotometric methods. Amongst many limitations, these methods do not directly measure the 3-hydroxyacyl-CoA produced, neither do they allow determination of its stereospecific configuration. We have developed a chiral HPLC method coupled with tandem mass spectrometry (MS) for the sensitive, direct, stereospecific and quantitative analysis of ECH-1/-2 reaction products, or R-/S-3-hydroxyalkanoates in general. The method is based on the reaction of the 3-hydroxyl group on the chiral carbon with 3,5-dimethylphenyl isocyanate, creating a urethane derivative which is then chirally resolved on a chiral HPLC column having 3,5-dimethylphenyl carbamate-derivatized cellulose as the chiral stationary phase. The resolved urethane derivatives are detected using tandem MS in the multiple reactions monitoring (MRM) negative electrospray ionization mode by monitoring the free hydroxy fatty acid fragment ion liberated from its parent urethane derivative. The method resolves the R-/S-enantiomers of 3-hydroxy fatty acid homologues ranging from C6 to C16. Using this method, the net ECH activity present in clarified cell lysates of the bacterium Pseudomonas aeruginosa cultivated in a rich medium was found to be of both ECH-1 and ECH-2. Interestingly, the clarified cell lysate of Escherichia coli cultivated also in a rich medium displayed mainly an ECH-1 (S-specific) activity. This method will facilitate the quantification and stereospecific characterization of ECHs, as well as the chiral lipid profiling of bacterial secondary metabolites containing hydroxyalkanoic acid moieties.

On the Combined Application of Iatroscan TLC-FID and GC-FID to Identify Total, Neutral, and Polar Lipids and Their Fatty Acids Extracted from Foods

An efficient separation and quantification of the individual neutral and polar lipid classes and their constituent fatty acids was achieved by the combination of two different detection techniques: Iatroscan TLC-FID and GC-FID. The solvent composition and ratio of development system, the sample size, the fidelity, and precision were tested in order to estimate the effectiveness of separation of individual neutral and polar lipid classes and the quantitative reproducibility of the Iatroscan TLC-FID technique. GC-FID method, with a high-quality capillary column, allowed sensitive and reproducible fatty acid qualitative and quantitative analyses, separation of fatty acid structural isomers (e.g., n-C16:0, iso-C16:0 and anteiso-C16:0), positional isomers (e.g., C18:1ω-9 and C18:1ω-7), geometrical isomers (cis-trans), and homologues (e.g., C16:0, C17:0, C18:0, etc.) in standards and complex lipid samples. Seventeen (17) lipid classes and fifty-two (52) saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were identified and quantified, respectively, in samples of standard lipid and fatty acid mixtures, simulating the composition of natural lipids and their fatty acid methyl esters in common foods. The wide number of applications establishes this combination of Iatroscan TLC-FID and GC-FID methods as a powerful tool for lipid class and fatty acid analysis of any fat origin.

Contributions of modern and dead organic carbon to individual fatty acid homologues in spring aerosols collected from northern Japan

Radiocarbon (14C) and stable carbon isotope ratios (δ13C) have been used as proxies to evaluate the contributions of modern/fossil carbon and marine/terrestrial organic matter, respectively, in geochemical samples. However, there are few such studies in atmospheric aerosols. Here, we measured 14C contents and δ13C of individual n‐fatty acids in an aerosol sample collected from northern Japan in spring 2001 during Asian dust season. Our results show that the distribution of fatty acids in the spring aerosols was characterized by a strong even/odd carbon number predominance with two maxima at C16 and C26. Their δ13C (range: −30.6 to −20.5‰) showed higher values (average: −24.5‰) for lower molecular weight (LMW) fatty acids (C16 − C19) and lower values (average: −29.7‰) for higher MW (HMW) fatty acids (C20 − C32). This difference suggests that LMW acids are mainly derived from lacustrine and/or marine algal sources whereas HMW acids are predominantly from terrestrial C3 higher plants. Δ14C values of fatty acids were found to range from −96.9 to +122.9‰ with lower values for HMW acids and higher values for LMW acids. LMW acids in the aerosols contain only modern carbon. In contrast, HMW acids ≥C24 were found to contain up to 9.7 wt% dead carbon, although their major portion (up to 92.3%) is composed of modern carbon. Backward trajectory analyses indicated that the source regions of the spring aerosols were dominated by central and north China (62%). This study suggests that the old fatty acids in the spring aerosols are most likely originated from the loess deposits in China via long‐range atmospheric transport over the western North Pacific, although their contribution to the aerosols was relatively small.

Temperature dependence of mycosubtilin homologue production in Bacillus subtilis ATCC6633

Bacillus subtilis ATCC6633 produces mycosubtilin, a non-ribosomally synthesized lipopeptide of the iturin family which presents antagonistic activities toward various phytopathogens. Different homologues with fatty acid moiety varying from C 15 to C 17 are usually co-produced, with their biological activities increasing with the number of carbons in the fatty acid chain. In the present report, we highlight that growth temperature modulates both the extent of mycosubtilin production and the relative abundance of the different homologues. A 30-fold increase in mycosubtilin production was observed when the temperature was decreased from 37 °C to 25 °C for both strain ATCC6633 and its derivative BBG100, a constitutive mycosubtilin overproducer. However, no significant difference in either the expression of the mycosubtilin synthetase encoding genes or in the intracellular synthetase concentration could be found, suggesting that the observed phenotype originated from a higher mycosubtilin synthetase turnover at lower temperature. We also point out that lower growth temperature leads to an increased proportion of odd-numbered fatty acid homologues as a consequence of de novo synthesis of C 17 anteiso fatty acid following cell adaptation to low temperatures.

Isolation, Fractionation, and Identification of Sucrose Esters from Various Oriental Tobaccos Employing Supercritical Fluids

Abstract Isolation, fractionation, and identification of sucrose esters from aged oriental tobacco employing supercritical fluids have been completed. Underivatized sucrose ester-rich extracts were obtained using supercritical CO2 at densities greater than 0.73 g/mL. Lower density CO2 provided extracts with notable amounts of tobacco derived material; yet, no detectable sucrose ester content. Preparative supercritical fluid chromatography (SFC) provided for an additional purification of the sucrose ester-enriched fraction after column optimization. Structural assignments of the SFC fractions were facilitated using gas chromatography/mass spectrometry (GC/MS) accompanied by N, O-bis(trimethylsilyl)trifluoroacetamide-dimethylformamide (BSTFA-DMF) derivatization of the free hydroxyl groups and high performance-liquid chromatography/mass spectrometry (HPLC/MS). From a relative quantitative perspective regardless of tobacco type, sucrose esters having an acetyl group on C6 of the glucose function (Group III) were in higher concentration compared to both the concentration observed for sucrose ester of Group I (acetyl group on C3 of fructose) and sucrose ester of Group II (no acetyl group on either glucose or fructose). Saturated fatty acid constituents were found to range from a maximum total of 18 carbons to a minimum total of 13 carbons. Unsaturated and isomeric fatty acid homologues were detected within the Group II sucrose ester.

Fermentation of high-protein plant biomass by introduction of lactic acid bacteria

Lactic acid bacteria displaying increased ability to produce lactic acid, medium proteolytic activity, and tolerance to osmotic stress were isolated under selective conditions from phyllosphere and rhizosphere of registered and raised cultivars of legumes. Lactic fermentation of poorly ensilable leguminous plants (red clover and Caucasian goat's rue) was performed by introduction of rifampin-resistant homofermenting representatives of the genus Lactobacillus (selected according to a set of technologically important characteristics). The results demonstrate that introduction of active local strains of lactobacteria, as well as the collection strain Lactobacillus plantarum BS 933, enhances activation of ensiling and increases the quality of fodder, as assessed according to the standard criteria (a decrease in pH of the medium, the ratio of lactic acid to fatty acid homologues, and the composition of silage microflora).

Variability of the fatty acid composition during development of the green microalga Apatococcus constipatus.

The green microalga Apatococcus constipatus was investigated for its fatty acid composition using GC and MS techniques. Considerable variations were found in individual fatty acid contents according to the stage of culture development. A set of saturated fatty acid homologues was distinguished as the main component regardless of the culture age. The occurrence of some uncommon fatty acids in minor amounts, such as hydroxylated ones, was found to be characteristic of the studied species. Depending on the development stage, those compounds were detected either only during initial growth phases or throughout the cultivation time.

Influence of phospholipid chain length on verotoxin/globotriaosyl ceramide binding in model membranes: comparison of a supported bilayer film and liposomes

The importance of the surrounding lipid environment on the availability of glycolipid carbohydrate for ligand binding was demonstrated by studying the influence of phosphatidylcholine fatty acid chain length on binding of verotoxins (VT1 and VT2c) to their specific cell surface receptor, globotriaosylceramide (Gb3) in the presence of auxiliary lipids both in a microtitre plate surface bilayer film and in a liposome membrane model system. In the microtitre assay, both VT1 and VT2c binding to Gb3 was increased as a function of decreasing PC acyl chain length likely resulting in increased Gb3 exposure. In the liposome assay VT1 binding was similarly modulated, however the effect of VT2c binding was more complex and did not follow a simple function of increased carbohydrate exposure. Earlier work established that C22:1 and C18:1Gb3 fatty acid homologues were the preferred Gb3 receptor containing liposomes, but in C14PC liposomes, binding to C22:1Gb3 (but not C18:1Gb3) was elevated such that this Gb3 species now became the preferred receptor for both toxins. This change in verotoxin/Gb3 homologue binding selectivity in the presence of C14PC did not occur in the microtitre bilayer format. These results are consistent with our proposal that these toxins recognize different epitopes on the Gb3 oligosaccharide. We infer that relative availability of these epitopes for toxin binding in an artificial bilayer is influenced not only by the exposure due to the discrepancy between the fatty acyl chain lengths of Gb3 and PC, but by the physical mode of presentation of the bilayer structure. Such acyl chain length differences have a more marked effect in a supported bilayer film whereas only the largest discrepancies affect Gb3 receptor function in liposomes. The basis of phospholipid modulation of glycolipid carbohydrate accessibility for receptor function is likely complex and will involve phase separation, gel/liquid crystalline transition, packing and lateral mobility within the bilayer, suggesting that such parameters should be considered in the assessment of glycolipid receptor function in cells.

13C-Nuclear magnetic resonance spectroscopic studies of triacylglycerols of type AAA containing ( Z)- and ( E)-monoethylenic acyl groups

The 13C-NMR properties of a total of 22 synthetic ( Z)-ethylenic and ( E)-ethylenic triacylglycerols of type AAA (containing isomeric positional unsaturated fatty acid homologues with the ethylenic bond located at Δ 2 to Δ 12 position) have been studied. The results show that the shifts of the glyceryl carbon atoms are only significantly affected when the unsaturated center is located at either the Δ 2 or Δ 3 position of the acyl chains. The ethylenic carbon atoms in the α- and β-acyl chains are fully resolved except in two cases, viz. 12:1(3 Z)/12:1(3 Z)/12:1(3 Z) and 15:1(6 E)/15:1(6 E)/15:1(6 E), where the shifts of the C-4 and C-7 ethylenic carbon atoms in the α- and β-acyl chains, respectively, remain unresolved. From the carbon chemical shift values of the ethylenic carbons and the difference between the shift values of these nuclei in the same acyl chain, it is possible to determine the position of the unsaturated center by this technique. Using the signal pattern displayed by the ethylenic carbon nuclei in the spectra, the positional distribution of short-chain fatty acid moieties in the glycerol ‘backbone’ can be determined. Methylene carbon atoms in the α- and β-acyl chain, which are located close to the acyl function are resolved up to the C-6 carbon atom. It is possible to locate the position of the unsaturated center in the acyl chains as remote as the Δ 12 position and the position (α- or β-acyl) of the unsaturated acyl chains on the glyceryl backbone of these triacylglycerol molecules by 13C-NMR spectroscopy.

Capillary zone electrophoretic determination of C 2C 18 linear saturated free fatty acids with indirect absorbance detection

The potential of capillary zone electrophoresis for the separation of linear saturated fatty acids in their free form was evaluated. With increasing chain length, difficulties arise from decreasing analyte solubility in aqueous media, increasing occurrence of analyte aggregation and decreasing separation selectivity between successive homologues. A solution was to use electrolytes containing cyclodextrins (CDs) and methanol. The separation of C 2C 14 fatty acid homologues differing in only one carbon atom was achieved in less than 10 min using a purely aqueous electrolyte with trimethyl-β-CD as an additive. The separation of C 7C 18 homologues was completed in under 20 min with electrolytes containing up to 60% methanol, in addition to the aforementioned CD. In the presence of the CD, analyte solubility is enhanced through the inclusion of the alkyl chain of the acid in the CD cavity, while separation selectivity is improved because the stability constants of the inclusion complexes increase with increasing chain length of the acid. The lack of a suitable chromophore moiety was circumvented through the optimization of indirect absorbance detection conditions. p-Anisate was selected as the chromogenic species. The minimum detectable concentrations are of the order of (1–2)·10 −6 mol l −1 (0.2–0.5 ppm) and detection linearity was established over at least three orders of magnitude of concentration. The quantitative analysis of a coco oil extract sample is presented, showing results almost identical with those obtained by gas chromatography. Owing to the close values for response factors resulting from the indirect detection principles, a rapid percentage composition can be obtained by corrected peak area normalization.

Glycosphingolipid receptor function is modified by fatty acid content. Verotoxin 1 and verotoxin 2c preferentially recognize different globotriaosyl ceramide fatty acid homologues

Verotoxins (VT) are a family of Escherichia coli-derived toxins which have been associated with hemolytic uremic syndrome, the leading cause of acute pediatric renal failure, and hemorrhagic colitis. Verotoxins (VT1 and VT2c) both show terminal gal alpha 1-4gal-dependent binding to globotriaosylceramide (Gal alpha 1-4Gal beta 1-4Glc-Cer; Gb3), yet VT2c shows a thousandfold lower specific cytotoxic activity in vitro. Our previous studies have shown this discrepancy is a function of the receptor binding B subunit and that VT1/Gb3 binding in a lipid matrix is affected by heterogeneity in the ceramide fatty acid chain length. The influence of the fatty acid composition of Gb3 on the binding of VT1 and VT2c has now been compared using 14 homogeneous semisynthetic Gb3 molecular species of differing fatty acid chain length and degree of saturation from C12 to C24. The binding of verotoxin was quantitated by Scatchard analysis using a solid-phase binding assay in the presence of auxiliary lipids, which may in some respects approximate to receptor function within the plasma membrane of sensitive cells. Differential binding was observed for several of these species in the lipid matrix, indicating that the fatty acid moiety of Gb3 is important for VT binding under such conditions. The short chain fatty acid containing Gb3 (C12 and C14) showed minimal binding. Middle and long chain fatty acid Gb3 homologues (C16, C18, C20, C22, and C24) were effectively recognized by VTs. The presence of an unsaturated fatty acid in Gb3 significantly increased VT binding in all cases. C20:0 and C22:1 containing Gb3 had the greatest capacity to bind VT1. In contrast, C18:0 and C18:1 homologues showed the greatest capacity for VT2c binding (higher than VT1). These results were, in general, reflected in cell cytotoxicity in that receptor-deficient cells reconstituted with C22:1Gb3 were maximally sensitive to VT1 in vitro whereas cells reconstituted with C18:1Gb3 were maximally sensitive to VT2c. VT2c was an ineffective inhibitor of 125I-VT1 binding to C22:1 Gb3 but in contrast, more effective than VT1 to compete binding to C18:1 Gb3. Similarly, VT1 was less effective than VT2c to compete binding of 125I-VT2c to C18:1 but more effective than VT2c to compete for C22:1 Gb3 binding. These results suggest that VT1 and VT2c bind selectively to different but overlapping carbohydrate epitopes on the Gb3 molecule which are differentially available in these Gb3 fatty acid homologues in a lipid environment.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of fatty acid sodium salts with sodium deoxycholate

Interaction of homologous fatty acids (C3-C18) with sodium deoxycholate was investigated. From NMR and ultrasonic results it was found that short chain homologues (up to C9) do not participate in the formation of mixed micelles with sodium deoxycholate. Fatty acid homologues with longer chains (starting with C9) form mixed micelles by "burying" hydrophobic chains in hydrophobic environment of a sodium deoxycholate micelle.

Biosynthesis of algal pheromones. A model study with the composite Senecio isatideus.

Several cyclic and alicyclic C11 hydrocarbons have been shown to act as gamete releasing and/or attracting pheromones during sexual reproduction of brown algae (Phaeophyceae). The same compounds are also found in the essential oils of various plants, of which the occurrence of the cycloheptadiene-pheromone ectocarpene in Senecio isatideus (Compositae) is noteworthy. Administration of [3H]dodeca-3,6,9-trienoic acid to cuttings of this plant leads to incorporation of radioactivity into ectocarpene. Double-bond-deuterated nona-3,6-dienoic acid is converted to fucoserratene, the pheromone of several Fucales, which is certainly not present among the hydrocarbons of Senecio. This proves that the pool of medium-chain, multiply unsaturated fatty acids includes precursors of all types of highly unsaturated hydrocarbons. Appropriately labelled (deuterium markers) fatty acid homologues were synthesized and applied to Senecio plantlets to unravel the mechanistic aspects. The results strongly suggest radical initiation of the pheromone biosynthesis by abstraction of a single hydrogen from a 1,4-pentadienyl segment of the fatty acid followed by oxidation to the corresponding cation. This causes fragmentation of the reactive intermediate into an olefine and carbon dioxide by neighbouring-group participation of the flanking double bonds. A tentative biosynthetic scheme is deduced from the experimental results which also sets the stereochemistry of the algal pheromones into a uniform mechanistic concept.

Uptake and metabolism of fatty acids by dispersed adult rat heart myocytes. II. Inhibition by albumin and fatty acid homologues, and the effect of temperature and metabolic reagents.

Uptake and metabolism of fatty acids by dispersed adult rat heart myocytes. II. Inhibition by albumin and fatty acid homologues, and the effect of temperature and metabolic reagents.

Direct quantitative gas chromatographic separation of C2-C6 fatty acids, methanol, and ethyl alcohol in aqueous microbial fermentation media.

A method is described for the direct quantitative gas chromatographic separation of C(2)-C(6) lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 muliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C(2)-C(6) acids added to culture supernatant fluids were obtained.

Direct Quantitative Gas Chromatographic Separation of C2-C6 Fatty Acids, Methanol, and Ethyl Alcohol in Aqueous Microbial Fermentation Media

A method is described for the direct quantitative gas chromatographic separation of C(2)-C(6) lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 muliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C(2)-C(6) acids added to culture supernatant fluids were obtained.